Alkylphenol-terminated copolycarbonates, processes for preparing the same, molding compositions containing the same, and articles prepared therefrom

ABSTRACT

Copolycarbonates comprising alkylphenolchain terminator groups for adjusting the molecular weight, compositions of these copolycarbonates with additives chosen from the group of heat stabilizers and mold release agents, the use thereof for the production of moldings and moldings obtained therefrom.

BACKGROUND OF THE INVENTION

Copolycarbonates belong to the group of industrial thermoplastics. Theyhave diverse uses in the electrical and electronics sector, as a housingmaterial for lamps and in uses where particular thermal and mechanicalproperties are required, for example hair driers, uses in the automobilesector, coverings of plastic, diffusing screens or light conductorelements and lamp coverings or lamp holders (bezels).

Good thermal and mechanical properties, such as Vicat temperature (heatdistortion temperature) and glass transition temperature, arepractically always necessarily required for these uses. In order toachieve the increased heat distortion temperature, specific bisphenols,which have an involved synthesis and are therefore also expensive, mustbe resorted to.

It is known that in the case of polymers these properties depend on themolecular weight. Generally, they increase with increasing molecularweight and approach a limit value. In this context, however, not onlythe molecular weight per se, but the molecular inhomogeneity factorU=(Mw/Mn)−1 is of importance. Large inhomogeneity factors can causenegative thermal and mechanical properties in copolycarbonates. Themolecular weight furthermore has a direct influence on the viscosity(solution and melt viscosity) and therefore on the flowability of apolymer melt at a given processing temperature. However, high molecularweight products flow more poorly and can therefore be processed onlywith significantly shorter cycle times. This route is therefore notfeasible for also fulfilling the necessary mechanical properties andheat distortion temperature at a relatively low molecular weight.Moreover, it is known, that low molecular weight compounds and oligomerscan have a negative impact on thermal and mechanical properties ofcopolycarbonates.

Alkylphenols, in particular p-tert-butylphenol (also referred tohereinafter as “BUP” for simplification), as chain terminators for thepreparation of polycarbonate are known (see, e.g., International Pat.Pub. No. WO 01/51541, European Pat. Pub. No. EP 1249463A andInternational Pat. Pub. No. WO 2004/063249, the entire contents of eachof which is hereby incorporated herein by reference). However, thepublications cited describe neither polycarbonates having a definedmolecular weight distribution nor the use of alkylphenols for thepreparation of copolycarbonates having a defined molecular weightdistribution. In particular, no indication of the influence of the chainterminator on the molecular inhomogeneity factor in a given copolymercomposition when phenol is used as the chain terminator nor on the Vicattemperature is to be found.

BRIEF SUMMARY OF THE INVENTION

The present invention relates, in general, to copolycarbonates having anarrow molecular weight distribution and compositions of thesepolycarbonates with additives chosen from the group of heat stabilizersand mold release agents, the use thereof for the production of moldingsand moldings obtainable therefrom and the use of alkylphenols foradjusting the molecular weight of copolycarbonates.

Various embodiments of the present invention provide aromaticpolycarbonates having an improved heat distortion temperature andmethods for their preparation, at a given/defined viscosity (solution ormelt viscosity), in a continuous process in which the content of lowmolecular weight compounds and oligomers is reduced, i.e. theinhomogeneity factor U=(Mw/Mn)−1 becomes smaller, and at the same timethe thermal properties (Vicat and glass temperature) are improved andthe amount of specific high T_(g) bisphenol employed is lower.

It has surprisingly been found that alkylphenols which are employed aschain terminators in the preparation of polycarbonates according tovarious embodiments of the present invention have a decisive influenceon the course of gel permeation chromatography (GPC) curves, i.e. on themolecular weight distribution, and therefore also on the content of lowmolecular weight compounds and oligomers which are to be avoided, andthe Vicat temperature for a given copolymer composition can beincreased. This measure for controlled improvement of the molecularweight distribution, i.e. narrower distribution or lower inhomogeneityfactor U=(Mw/Mn)−1, and the adjustment thereof and dependency on thenature of the chain terminator in a continuous process by theinterfacial process, was hitherto unknown. Moreover, it was found thatthe same high level Vicat- and glass temperature can be achieved withsmaller amounts of the special high-T_(g)-Bisphenols if a narrowermolecular weight distribution is provided, as in the present invention.At the same time, a lower melt viscosity and, hence an improvedprocessing behavior of the resulting copolycarbonates in an injectionmolding process is obtained.

This represents an important criterion for the mechanical and thermalperformance of the injection moulded or extruded component. Injectionmoulded parts or extrudates produced from the copolycarbonates andcopolycarbonate compositions according to the invention havesignificantly improved thermal properties (glass transition temperatureTg and Vicat temperature).

The present invention provides copolycarbonates containing as a chainterminator (end group) a structural unit of the formula (1)

in which R1 and R2 independently of one another represent hydrogen or aC₁-C₁₈-alkyl, but wherein R1 and R2 cannot simultaneously be hydrogen,and at least one diphenol unit of the formula (2)

in which R³ represents C₁-C₄-alkyl, preferably methyl, R⁴ representshydrogen or C₁-C₄-alkyl, preferably methyl, n represents 0, 1, 2 or 3,preferably 2 or 3, m represents 0, 1 or 2, preferably 0, wherein thecopolycarbonates have the following inhomogeneity factors, depending onthe molecular weight range:

A) copolycarbonates having a content of ≧50 mol % and of <100 mol % ofdiphenol unit of the formula (2), based on the sum of the diphenols: forlinear copolycarbonates (“CoPC”) having an average molecular weight(weight-average) of from 18,000 to 35,000 g/mol, U=(Mw/Mn)−1 is 1.3 to2.5, preferably 1.4 to 2.3, very particularly preferably 1.5 to 2.3.

B) copolycarbonates having a content of greater than 0 and less than 50mol % of diphenol unit of the formula (2), based on the sum of thediphenols: for linear CoPC having an average molecular weight(weight-average) of from 16,000 to 35,000 g/mol, U=(Mw/Mn)−1 is 1.2 to2.4, preferably 1.2 to 2.2, particularly preferably 1.2 to 2.0 and veryparticularly preferably 1.2 to 1.8.

In formula (1), R1 and R2 independently of one another preferablyrepresent hydrogen or alkyl having 1 to 8, particularly preferablyhaving 1 to 4 carbon atoms, with the proviso that R1 and R2 are notsimultaneously hydrogen. Tert-Butylphenol or n-butylphenol is veryparticularly preferred, in particular p-tert-butylphenol.

Thermoplastic aromatic polycarbonates in the context of the presentinvention include both homopolycarbonates and copolycarbonates; whereinin the context of the various embodiments of the present invention,homopolycarbonates from the diphenol unit of the formula (2) are alsosubsumed under the term copolycarbonate.

The thermoplastic copolycarbonates have the abovementioned molecularweights M_(w) (weight-average Mw, determined by GPC measurement,polycarbonate calibration). Molecular weights can also be stated by thenumber-average Mn, which is likewise determined by means of GPC afterprior calibration for polycarbonate.

The inhomogeneity factor U=(Mw/Mn)−1, as a measure of the molecularweight distribution of the copolycarbonates, can thus be determined forvarious molecular weight ranges.

One embodiment of the present invention includes copolycarbonatescomprising: (i) a chain terminator structural unit of the formula (1):

wherein R1 and R2 each independently represent hydrogen or aC₁₋₁₈-alkyl, with the proviso that R1 and R2 are not simultaneouslyhydrogen; and (ii) at least one diphenol unit of the formula (2)

wherein R³ represents a C₁₋₄-alkyl, R⁴ represents hydrogen orC₁-C₄-alkyl, preferably methyl, and n represents 0, 1, 2 or 3; and

wherein the copolycarbonates have an inhomogeneity factor of: A) 1.3 to2.5, when the copolycarbonates have a content of ≧50 mol % and <100 mol% of the at least one diphenol unit of the formula (2), based on totaldiphenols, and have an average molecular weight (weight-average) of18,000 to 35,000 g/mol; and B) 1.2 to 2.0, when the copolycarbonateshave a content of greater than 0 and less than 50 mol % of the at leastone diphenol unit of the formula (2), based on total diphenols, and havean average molecular weight (weight-average) of 16,000 to 35,000 g/mol.

Various embodiments of the present invention furthermore includecompositions comprising:

(C) abovementioned copolycarbonate with alkylphenol of the formula (1)as an end group, wherein the inhomogeneity factor has the abovementionedvalues, depending on the molecular weight range, and

(D) at least one additive chosen from the group consisting of heatstabilizer, mould release agent and UV stabilizer.

The compositions, in general, can comprise 0.001 to 1 wt. %, preferably0.005 to 0.9, particularly preferably 0.005 to 0.8 wt. %, veryparticularly preferably 0.04 to 0.8 wt. %, and even more preferably 0.04to 0.6 wt. % (based on the total composition) of additives according tocomponent D).

Tris-(2,4-di-tert-butylphenyl)phosphite (Irgafos 168),Tetrakis(2,4-di-tert.-butylphenyl)[1,1biphenyl]-4,4′-diylbisphosphonite,Trisoctylphosphat, Octadecyl-3-(3,5-di-tertbutyl-4-hydroxyphenyl)propionat (Irganox 1076),Bis(2,4-dicumylphenyl)-pentaerythritoldiphosphite (Doverphos S-9228),Bis(2,6-di-tert.butyl-4-methyl-phenyl)pentaerythritoldiphosphite (ADKSTAB PEP-36) or Triphenylphosphine are preferably suitable as heatstabilizer. They are employed by themselves or in a mixture (e.g.Irganox B900 or Doverphos S-92228 with Irganox B900 resp. Irganox 1076).

Pentaerythritol tetrastearate, glycerol monostearate, stearyl stearateor propanediol mono- or distearate are preferably suitable as the mouldrelease agent. They are employed by themselves or in a mixture.

2-(2′-Hydroxyphenyl)benzotriazoles, 2-hydroxybenzophenones, esters ofsubstituted and unsubstituted benzoic acids, acrylates, stericallyhindered amines, oxamides and 2-(2-hydroxyphenyl)-1,3,5-triazines arepreferably suitable as UV stabilizers, and substituted benzotriazolesare particularly preferred.

Other various embodiments of the present invention include methods offorming molded and/or extruded articles using copolycarbonates and/orcompositions containing such according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

As used herein, the singular terms “a” and “the” are synonymous and usedinterchangeably with “one or more” and “at least one,” unless thelanguage and/or context clearly indicates otherwise. Accordingly, forexample, reference to “a diphenol” herein or in the appended claims canrefer to a single diphenol or more than one diphenol. Additionally, allnumerical values, unless otherwise specifically noted, are understood tobe modified by the word “about.”

Copolycarbonates according to the various embodiments of the inventioncan be prepared by a continuous interfacial process. The preparation ofthe copolycarbonates to be used according to the invention is inprinciple carried out in a known manner from diphenols, carbonic acidderivatives and optionally branching agents.

Processes for polycarbonate synthesis are generally known and aredescribed in numerous publications. For example, EP-A 0 517 044, WO2006/072344, EP-A 1 609 818, WO 2006/072344 and EP-A 1 609 818, theentire contents of each of which are hereby incorporated herein byreference, describe the interfacial and the melt process for thepreparation of polycarbonate.

However, it cannot be deduced from the prior art what measures mustalready be taken during the synthesis in order to obtain a polycarbonatehaving a very good notched impact strength and improved heat distortiontemperature in a continuous process. In particular, no indication of theinfluence of the chain terminator on the inhomogeneity factor U wasknown.

In a continuous process for the preparation of aromatic polycarbonatesor copolycarbonates having a relatively narrow molecular weightdistribution by the so-called interfacial process, according to variousembodiments of the present invention, the phosgenation of a disodiumsalt of a mixture of various bisphenols initially introduced into thereaction vessel in an aqueous alkaline solution (or suspension) iscarried out in the presence of an inert organic solvent or, preferably,a solvent mixture, which forms a second phase. The oligocarbonatesformed, which are chiefly present in the organic phase, undergocondensation with the aid of suitable catalysts to give copolycarbonateshaving the desired molecular weight dissolved in the organic phase. Theorganic phase is finally separated off and the copolycarbonate isisolated therefrom by various working up steps, preferably by adevolatilization extruder or extrusion evaporator. The decisive step foracquiring products having an improved heat distortion temperatureconsists of carrying out this continuous process such that the narrowestpossible molecular weight distribution of the polycarbonate, i.e. a lowinhomogeneity factor, is already obtained during the synthesis andwithout specific working up, such as e.g. precipitation or sprayevaporation. This is achieved according to the invention by the suitablechoice of the chain terminator, which leads to a lower inhomogeneityfactor.

Apart from the diphenols of the formula (2), dihydroxyaryl compoundswhich are suitable for the preparation of the copolycarbonates are thoseof the formula (3)HO—Z—OH  (3)in which Z is an aromatic radical having 6 to 30 C atoms, which cancontain one or more aromatic nuclei, can be substituted and can containaliphatic or cycloaliphatic radicals or alkylaryls or hetero atoms asbridge members.

Preferably, in formula (3) Z represents a radical of the formula (3 a)

in which R⁶ and R⁷ independently of one another represent H,C₁-C₁₈-alkyl, C₁-C₁₈-alkoxy, halogen, such as Cl or Br, or in each caseoptionally substituted aryl or aralkyl, preferably H or C₁-C₁₂-alkyl,particularly preferably H or C₁-C₈-alkyl and very particularlypreferably H or methyl, and X represents —SO₂—, —CO—, —O—, —S—, C₁— toC₆-alkylene, C₂— to C₅-alkylidene or C₆— to C₁₂-arylene, which canoptionally be condensed with further aromatic rings containing heteroatoms.

Preferably, X represents C₁ to C₅-alkylene, C₂ to C₅-alkylidene, —O—,—SO—, —CO—. —S—, —SO₂—, isopropylidene or oxygen, in particularisopropylidene.

For the preparation of the copolycarbonates according to the invention,1,1-bis-(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane (bisphenol TMC) and1,1-bis-(3-methyl-4-hydroxyphenyl)-3,3,5-trimethyloyclohexane (dimethylTMC) are preferred as a diphenol derived from formula (2).

Diphenols of the formula (3) which are suitable for the preparation ofthe copolycarbonates to be used according to the invention are, forexample, hydroquinone, resorcinol, bis-(hydroxyphenyl)-alkanes,bis-(hydroxyphenyl)sulfides, bis-(hydroxyphenyl)ethers,bis-(hydroxyphenyl)ketones, bis-(hydroxyphenyl)sulfones,bis-(hydroxyphenyl)sulfoxides,α,α′-bis-(hydroxyphenyl)-diisopropylbenzenes, and alkylated,nucleus-alkylated and nucleus-halogenated compounds thereof.

Preferred diphenols are 4,4′-dihydroxydiphenyl,2,2-bis-(4-hydroxyphenyl)-1-phenylpropane,1,1-bis-(4-hydroxyphenyl)-phenylethane,2,2-bis-(4-hydroxyphenyl)-propane,2,2-bis-(3-methyl-4-hydroxyphenyl)-propane,2,4-bis-(4-hydroxyphenyl)-2-methylbutane,1,3-bis-[2-(4-hydroxyphenyl)-2-propyl]-benzene (bisphenol M),2,2-bis-(3-methyl-4-hydroxyphenyl)-propane,bis-(3,5-dimethyl-4-hydroxyphenyl)-methane,2,2-bis-(3,5-dimethyl-4-hydroxyphenyl)-propane,bis-(3,5-dimethyl-4-hydroxyphenyl)sulfone,2,4-bis-(3,5-dimethyl-4-hydroxyphenyl)-2-methylbutane and1,3-bis-[2-(3,5-dimethyl-4-hydroxyphenyl)-2-propyl]-benzene.

Particularly preferred diphenols are 2,2-bis-(4-hydroxyphenyl)-propane(BPA) and 2,2-bis-(3-methyl-4-hydroxyphenyl)-propane (dimethyl BPA).

Copolycarbonates from bisphenol A and bisphenol TMC and copolycarbonatesfrom dimethyl BPA and bisphenol TMC or BPA and dimethyl TMC areparticularly preferred.

These and further suitable diphenols are commercially obtainable and aredescribed e.g. in “H. Schnell, Chemistry and Physics of Polycarbonates,Interscience Publishers, New York 1964, p. 28 et seq.; p. 102 et seq.”,and in “D. G. Legrand, J. T. Bendler, Handbook of Polycarbonate Scienceand Technology, Marcel Dekker New York 2000, p. 72 et seq.”.

Random copolycarbonates having the following structure:

wherein R represents C₁-C₆-alkyl, preferably C₁-C₄-alkyl, x and ycharacterize the mol % of the bisphenols employed and therefore the sumof x+y=1 and x and y independently of one another denote values of from0 to 1, preferably 0.01 to 0.99, particularly preferably 0.02 to 0.98,very particularly preferably from 0.03 to 0.97, and n is determined bythe molecular weight, are particularly preferred.

Random copolycarbonates having the following structure:

wherein R denotes methyl and x and y denote values of from 0 to 1,preferably 0.01 to 0.99, particularly preferably from 0.02 to 0.98, veryparticularly preferably from 0.03 to 0.97, are very particularlypreferred.

The thermoplastic copolycarbonates, including the thermoplastic aromaticpolyester carbonates, have molecular weights M_(w) (weight-average Mw,determined by gel permeation chromatography GPC measurement) of from12,000 to 120,000, preferably from 15,000 to 80,000, in particular from18,000 to 60,000, very particularly preferably from 18,000 to 40,000g/mol. Molecular weights can also be stated by the number-average Mn,which is likewise determined by means of GPC after prior calibration forpolycarbonate.

The diphenols used, like all the other chemicals and auxiliarysubstances added to the synthesis, may be contaminated with impuritiesoriginating from their own synthesis, handling and storage. However, itis desirable to work with raw materials which are as pure as possible.

An aqueous phase of NaOH, one or more bisphenols and water is used inthis process, it being possible for the concentration of this aqueoussolution with respect to the sum of the bisphenols, calculated not asthe sodium salt but as the free bisphenol, to vary between 1 and 30 wt.%, preferably between 3 and 25 wt. %, particularly preferably between 3and 8 wt. % for polycarbonates having an Mw>45,000 and 12 to 22 wt. %for polyearbonates having an Mw<45,000. In this context, at higherconcentrations it may be necessary to heat the solutions. The sodiumhydroxide used to dissolve the bisphenols can be used as a solid or asaqueous sodium hydroxide solution. The concentration of the sodiumhydroxide solution depends on the target concentration of the requiredbisphenolate solution, but as a rule is between 5 and 25 wt. %,preferably 5 and 10 wt. %, or a higher concentration is chosen and thesolution is subsequently diluted with water. In the process withsubsequent dilution, sodium hydroxide solutions having concentrations ofbetween 15 and 75 wt. %, preferably 25 and 55 wt. %, optionally heated,are used. The alkali content per mol of bisphenol depends greatly on thestructure of the bisphenol, but as a rule varies between 0.25 mol ofalkali/mol of bisphenol and 5.00 mol of alkali/mol of bisphenol,preferably 1.5-2.5 mol of alkali/mol of bisphenol. The bisphenols can bedissolved together. However, it may be advantageous to dissolve thebisphenols separately in an optimum alkaline phase and to meter thesolutions separately or to feed them to the reaction in combined form.It may furthermore be advantageous to dissolve the bisphenol orbisphenols not in sodium hydroxide solution but in dilute bisphenolatesolution provided with additional alkali. The dissolving operations canstart from solid bisphenol, usually in flakes or prill form, or alsofrom molten bisphenol. The sodium hydroxide employed or the sodiumhydroxide solution can have been prepared by the amalgam process or theso-called membrane process. Both processes have been used for a longtime and are familiar to the person skilled in the art. Sodium hydroxidesolution from the membrane process is preferably used.

The aqueous phase prepared in this way is phosgenated together with anorganic phase comprising solvents for polycarbonate which are inerttowards the reactants and form a second phase.

The metering of bisphenol optionally practised after or during theintroduction of phosgene can be carried out for as long as phosgene orits direct secondary products, the chlorocarbonic acid esters, arepresent in the reaction solution.

The synthesis of copolycarbonates from bisphenols and phosgene in analkaline medium is an exothermic reaction and is carried out in atemperature range of from −5° C. to 100° C., preferably 15° C. to 80°C., very particularly preferably 25-65° C., it being necessary, whereappropriate, to work under increased pressure, depending on the solventor solvent mixture.

The organic phase can comprise one or mixtures of several solvents,mixtures being preferred. Suitable solvents are chlorinated hydrocarbons(aliphatic and/or aromatic), preferably methylene chloride,trichloroethylene, 1,1,1-trichloroethane, 1,1,2-trichloroethane andchlorobenzene and mixtures thereof. However, aromatic hydrocarbons, suchas benzene, toluene or m/p/o-xylene, or aromatic ethers, such asanisole, by themselves, in a mixture or additionally to or in a mixturewith chlorinated hydrocarbons, can also be used. Another embodiment ofthe synthesis uses solvents which do not dissolve but only swellpolycarbonate. Non-solvents for polycarbonate in combination withsolvents can therefore also be used. In this case, solvents which aresoluble in the aqueous phase, such as tetrahydrofuran, 1,3/1,4-dioxaneor 1,3-dioxolane, can also be used as solvents if the solvent partnerforms the second organic phase. However, mixtures of methylene chlorideand chlorobenzene having a mixture ratio (weight ratio) of from 60:40 to55:45 are preferred.

The two phases which form the reaction mixture are mixed in order toaccelerate the reaction. This is effected by introduction of energy viashear forces, i.e. pumps or stirrers, or by static mixers or bygeneration of turbulent flow by means of nozzles and/or diaphragms.Combinations of these measures are also used, often also repeatedly in asequence of time or apparatus. Anchor, propeller and MIG stirrers etc.,such as are described e.g. in Ullmann, “Encyclopedia of IndustrialChemistry”, 5th edition, vol. B2, p. 251 et seq., are preferablyemployed as stirrers. Centrifugal pumps, often also multi-stage, 2- to9-stage pumps being preferred, are employed as pumps. Nozzles and/ordiaphragms which are employed are perforated diaphragms or pipe piecesnarrowed at the position thereof or also Venturi or Lefos nozzles.

The phosgene can be introduced in gaseous or liquid form or dissolved ina solvent. The excess of phosgene used, based on the sum of thebisphenols employed, is between 3 and 100 mol %, preferably between 5and 50 mol %. In this case, the pH of the aqueous phase is kept in thealkaline range, preferably between 8.5 and 12, during and after themetering of phosgene via topping up of sodium hydroxide solution once orseveral times or corresponding topping up of bisphenolate solution,while it should preferably be 10 to 14 after the addition of catalyst.The temperature during the phosgenation is 25 to 85° C., preferably 35to 65° C., it also being possible to work under increased pressure,depending on the solvent used.

The metering of phosgene can take place directly into the mixture oforganic and aqueous phase described, or also completely or partly,before mixing of the phases, into one of the two phases, which issubsequently mixed with the corresponding other phase. The phosgene canfurthermore be metered completely or partly into a recycled part streamof the synthesis mixture of two phases, this part stream preferablybeing recycled before addition of the catalyst. In another embodiment,the aqueous phase described is mixed with the organic phase containingthe phosgene and then added to the abovementioned recycled part streamafter a dwell time of from 1 second to 5 min, preferably 3 seconds to 2minutes, or the two phases, the aqueous phase described with the organicphase containing the phosgene, are mixed directly in the abovementionedrecycled part stream. In all these embodiments, the pH ranges describedabove are to be observed and if appropriate maintained by topping up ofsodium hydroxide solution once or several times or corresponding toppingup of bisphenolate solution. The temperature range must likewise bemaintained, where appropriate by cooling or dilution.

The copolycarbonate synthesis is carried out continuously. The reactioncan therefore be carried out in pumped circulation reactors, tubereactors or stirred tank cascades or combinations thereof where it is tobe ensured, by using the mixing organs already mentioned, that theaqueous and organic phase as far as possible only demix when thesynthesis mixture has reacted completely, i.e. no longer containshydrolysable chlorine from phosgene or chlorocarbonic acid esters.

The monofunctional chain terminators of the formula 1 or mixturesthereof required for regulation of the molecular weight, as such or inthe form of their chlorocarbonic acid esters, either are fed to thereaction with the bisphenolate or the bisphenolates, or are added at anydesired point in time of the synthesis, as long as phosgene orchlorocarbonic acid end groups are still present in the reaction mixtureor, in the case of the acid chlorides and chlorocarbonic acid esters aschain terminators, as long as sufficient phenolic end groups of thepolymer formed are available. Preferably, however, the chain terminatoror terminators are added after the phosgenation at a site or at a pointin time where phosgene is no longer present, but the catalyst has notyet been metered, or they are metered before the catalyst, together withthe catalyst or parallel therewith.

The amount of chain terminators to be employed is 0.5 mol % to 10 mol %,preferably 1 mol % to 8 mol %, particularly preferably 2 mol % to 6 mol%, based on the moles of the particular diphenols employed. The additionof the chain terminators can be carried out before, during or after thephosgenation, preferably as a solution in a solvent mixture of methylenechloride and chlorobenzene (8-15 wt. % strength).

The catalysts used in the interfacial synthesis are tertiary amines, inparticular triethylamine, tributylamine, trioctylamine,N-ethylpiperidine, N-methylpiperidine or N-i/n-propylpiperidine,particularly preferably triethylamine and N-ethylpiperidine. Thecatalysts can be added to the synthesis individually, in a mixture oralso side by side and successively, optionally also before thephosgenation, but meterings after the introduction of phosgene arepreferred. Metering of the catalyst or catalysts can be carried out insubstance, in an inert solvent, preferably that of the polycarbonatesynthesis, or also as an aqueous solution, in the case of the tertiaryamines then as ammonium salts thereof with acids, preferably mineralacids, in particular hydrochloric acid. If several catalysts are used orpart amounts of the total amount of the catalyst are metered, it is ofcourse also possible to carry out different methods of metering atvarious sites or various times. The total amount of catalysts used isbetween 0.001 to 10 mol %, based on the moles of bisphenols employed,preferably 0.01 to 8 mol %, particularly preferably 0.05 to 5 mol %.

After introduction of the phosgene, it may be advantageous to thoroughlymix the organic phase and the aqueous phase for a certain time before,where appropriate, the branching agent, if this is not metered togetherwith the bisphenolate, chain terminator and catalyst are added. Such anafter-reaction time may be advantageous after each metering. Theseafter-stirring times, if they are inserted, are between 10 seconds and60 minutes, preferably between 30 sec and 40 minutes, particularlypreferably between 1 and 15 min. These then take place in dwellreactors.

The at least two-phase reaction mixture which has reacted completely andcontains at most traces (<2 ppm) of chlorocarbonic acid esters isallowed to settle for separation of the phases. The aqueous alkalinephase may be passed completely or partly back into the polycarbonatesynthesis as aqueous phase, or is fed to waste water treatment, wheresolvent and catalyst contents are separated off and recycled. In anothervariant of the working up, after the organic impurities, in particularsolvents and polymer residues, have been separated off and optionallyafter adjustment to a certain pH, e.g. by addition of sodium hydroxidesolution, the salt is separated off, and e.g. can be fed to chlor-alkalielectrolysis, while the aqueous phase is optionally fed back to thesynthesis.

The organic phase containing the polymer must now be purified from allcontamination of an alkaline, ionic or catalytic nature.

Even after one or more settling operations, optionally assisted by flowsthrough settling tanks, stirred tanks, coalescers or separators orcombinations of these measures—it being possible for water optionally tobe metered into each or some of the separating steps, under certaincircumstances using active or passive mixing organs—the organic phasestill contains contents of the aqueous alkaline phase in fine dropletsand the catalyst, as a rule a tertiary amine.

After this coarse separating off of the alkaline aqueous phase, theorganic phase is washed once or several times with dilute acids,mineral, carboxylic, hydroxycarboxylic and/or sulfonic acids. Aqueousmineral acids, in particular hydrochloric acid, phosphorous acid andphosphoric acid or mixtures of these acids are preferred. Theconcentration of these acids should be in the range of 0.001 to 50 wt.%, preferably 0.01 to 5 wt. %.

The organic phase is furthermore washed repeatedly with desalinated ordistilled water. The organic phase, where appropriate dispersed withparts of the aqueous phase, is separated off after the individualwashing steps by means of settling tanks, stirred tanks, coalescers orseparators or combinations of these measures, it being possible for thewash water to be metered between the washing steps, optionally usingactive or passive mixing organs.

Acids, preferably dissolved in the solvent on which the polymer solutionis based, can optionally be added between these washing steps or alsoafter the washing. Preferably, hydrogen chloride gas and phosphoric acidor phosphorous acid, which can optionally also be employed as mixtures,are used here.

After the last separating operation, the purified polymer solutionobtained in this way should contain not more than 5 wt. %, preferablyless than 1 wt. %, very particularly preferably less than 0.5 wt. % ofwater.

The polymer can be isolated from the solution by evaporation of thesolvent by means of heat, vacuum or a heated entraining gas.

If the concentration of the polymer solution and where appropriate alsothe isolation of the polymer are carried out by distilling off thesolvent, optionally by superheating and letting down, a “flash process”is referred to, see also “Thermische Trennverfahren”, VCH Verlagsanstalt1988, p. 114; if instead of this a heated carrier gas is sprayedtogether with the solution to be evaporated, “spray evaporation/spraydrying” is referred to, described by way of example in Vauck,“Grundoperationen chemischer Verfahrenstechnik”, Deutscher Verlag fürGrundstoffindustrie 2000, 11th edition, p. 690. All these processes aredescribed in the patent literature and in textbooks and are familiar tothe person skilled in the art.

In the removal of the solvent by heat (distilling off) or theindustrially more effective flash process, highly concentrated polymermelts are obtained. In the known flash process, polymer solutions arerepeatedly heated under slightly increased pressure to temperaturesabove the boiling point under normal pressure, and these solutions,which are superheated with respect to normal pressure, are then let downinto a vessel under a lower pressure, e.g. normal pressure. In thiscontext it may be advantageous not to allow the concentration stages, orin other words the heating stages of the superheating, to become toogreat, but preferably to choose a two- to four-stage process.

The residues of the solvent can be removed from the highly concentratedpolymer melts obtained in this way either directly from the melt usingdevolatilization extruders (BE-A 866 991, EP-A 0 411 510, U.S. Pat. No.4,980,105, DE-A 33 32 065), thin film evaporators (EP-A 0 267 025),falling film evaporators or extrusion evaporators or by frictioncompacting (EP-A 0 460 450), optionally also with the addition of anentraining agent, such as nitrogen or carbon dioxide, or using vacuum(EP-A 0 039 96, EP-A 0 256 003, U.S. Pat. No. 4,423,207), oralternatively also by subsequent crystallization (DE-A 34 29 960) andthorough heating of the residues of the solvent in the solid phase (U.S.Pat. No. 3,986,269, DE-A 20 53 876).

Granules are obtained, if possible, by direct spinning of the melt andsubsequent granulation, or by using melt extruders, from which spinningis carried out in air or under liquid, usually water. If extruders areused, additives can be added to the melt, before this extruder,optionally using static mixers, or through side extruders in theextruder.

Cooling, spinning, granulation and subsequent transportation orconveying of the granules with gas or liquid, and subsequent storage,optionally after a thorough mixing or homogenizing process, are to beconfigured such that as far as possible, in spite of the static chargepossibly present, no impurities are applied to the polymer, strand orgranule surface, such as, for example, dust, abraded material from themachines, aerosol-like lubricants and other liquids, as well as saltsfrom water baths or cooling systems possibly used.

The materials obtained in this way are, as described for sprayevaporation, processed to granules and optionally provided withadditives.

The addition of additives serves to prolong the duration of use or thecolour (stabilizers), to simplify the processing (e.g. mould releaseagents, flow auxiliaries, antistatics) or to adapt the polymerproperties to exposure to certain stresses (impact modifiers, such asrubbers; flameproofing agents, colouring agents, glass fibres).

These additives can be added to the polymer melt individually or in anydesired mixtures or several different mixtures, and in particulardirectly during isolation of the polymer or after melting of granules ina so-called compounding step. In this context, the additives or mixturesthereof can be added to the polymer melt as a solid, that is to say as apowder, or as a melt. Another type of metering is the use ofmasterbatches or mixtures of masterbatches of the additives or additivemixtures.

Suitable additives are described, for example, in “Additives forPlastics Handbook, John Murphy, Elsevier, Oxford 1999”, in the “PlasticsAdditives Handbook, Hans Zweifel, Hanser, Munich 2001” or in WO99/55772, p. 15-25.

Conventional additives are, for example, fillers, UV stabilizers, heatstabilizers which differ from component B), antistatics, pigments, mouldrelease agents which differ from component B), flow auxiliaries andflameproofing agents. For example, alkyl and aryl phosphites, phosphatesor -phosphanes, low molecular weight carboxylic acid esters, halogencompounds, salts, chalk, quartz flour and glass and carbon fibres andcombinations thereof can be employed.

Colouring agents, such as organic dyestuffs or pigments, or inorganicpigments, IR absorbers, individually, in a mixture or also incombination with stabilizers, glass (hollow) beads, inorganic fillers ororganic or inorganic scattering pigments can furthermore be added.

The polycarbonates and polycarbonate compositions according to theinvention can be processed in the conventional manner on conventionalmachines, for example on extruders or injection moulding machines, togive any desired shaped articles, or mouldings to give films or sheetsor bottles.

The polycarbonates having a narrow molecular weight distributionaccording to the present invention which are obtainable in this way andpolycarbonate compositions obtainable therefrom can be employed for theproduction of extrudates (sheets, films and laminates thereof; e.g. forcard uses and tubes) and shaped articles (bottles), in particular thosefor use in the transparent sector, especially in the field of opticaluses, such as e.g. sheets, multi-wall sheets, glazing, diffusing orcovering screens, lamp coverings, covering screens of plastic, lightconductor elements or optical data storage media, such as audio CD,CD-R(W), DVD, DVD-R(W), minidisks in their various only readable oronce-writable and optionally also rewritable embodiments, and datacarriers for near-field optics. Furthermore for the production ofobjects for the E/E and IT sector.

The polycarbonate compositions are used in particular for thepreparation of compounds, blends and components in which thermal andmechanical properties are utilized, such as, for example, housings,objects in the E/E sector, such as plugs, switches, panels and lampholders and coverings, the automobile sector, such as lamp holders andcoverings and glazing, the medical sector, such as dialysers, connectorsand taps, and packaging, such as bottles and containers.

The present application likewise provides the extrudates and shapedarticles or mouldings from the polymers according to the invention.

Further possible uses of the polycarbonate moulding compositionsaccording to the invention are safety screens, which are known to berequired in many areas of buildings, vehicles and aircraft, and asshields for helmets. Production of extruded and solvent films fordisplays or electric motors, also ski foils. Production of blowmouldings, such as water bottles (see, for example, U.S. Pat. No.2,964,794). Production of transparent sheets, in particular hollowsheets, for example for covering buildings, such as stations,greenhouses and lighting installations. For the production of trafficlight housings or traffic signs. For the production of foams (see, forexample, DE-B 1 031 507). For the production of filaments and wires(see, for example, DE-B 1 137 167 and DE-A 1 785 137). As translucentplastics with a content of glass fibres for lighting purposes (see, forexample, DE-A 1 554 020). For the production of small precisioninjection mouldings, such as, for example, lens holders. For this,polycarbonates having a content of glass fibres which optionallyadditionally contain about 1 to 10 wt. % of MoS₂, based on the totalweight, are used. Optical uses, such as optical storage media (CD, DVD),safety glasses or lenses for photographic and film cameras (see, forexample, DE-A 2 701 173). Light transmitters, in particular as lightconductor cables (see, for example, EP-A1 0 089 801). As electricalinsulation materials for electrical conductors and for plug housings andplug connectors. As carrier material for organic photoconductors. Forthe production of lamps, e.g. searchlights, as so-called “head-lamps” orscattered light screens or lamp coverings. For medical uses, e.g.oxygenators, dialysers. For foodstuffs uses, such as e.g. bottles,tableware and chocolate moulds. For uses in the automobile sector wherecontact with fuels and lubricants may occur. For sports articles, suchas e.g. slalom poles. For household articles, such as e.g. kitchen sinksand letterbox housings. For housings, such as e.g. electricaldistribution cabinets, electrical equipment, domestic appliances,components of household articles, electrical and electronic equipment.For the production of motor cycle and safety helmets. Automobilecomponents, such as glazing, dashboards, vehicle body components andshock absorbers. For other uses, such as e.g. fattening stable doors oranimal cages.

The invention will now be described in further detail with reference tothe following non-limiting examples.

EXAMPLES Examples 1 to 3 Preparation of Copolycarbonates from BisphenolA and Bisphenol TMC

Various copolycarbonates each with different molecular weightdistributions were prepared by varying the chain terminator in acontinuous interfacial process (see Table 1). The composition of thecomonomers is in all cases the bisphenols BPA to bisphenol TMC in theweight ratio of 33 to 67% by weight (i.e. molar ratio of 40 to 60 mol%).

The reaction is conducted continuously in an emulsion comprising asolvent mixture, composed of 50.0 wt. % of methylene chloride and 50.0wt. % of chlorobenzene, and water. P-tert-Butylphenol (BUP) and phenol(PHE) are employed as chain terminators. N-Ethylpiperidine (EPP) is usedas the catalyst. The continuous reaction is operated until adequateamounts of the polycarbonate solution collected have formed. Thispolycarbonate solution formed, after the aqueous phase has beenseparated off, is washed under acidic conditions with hydrochloric acid,and then washed under neutral conditions until free from salts withcompletely desalinated water by means of disc separators. Thepolycarbonate solutions washed in this way are concentrated to aconcentration of 60-70 wt. % of polycarbonate in a multi-stage thermalpre-evaporation. The residual solvent is evaporated off via adevolatilization extruder and the resulting polycarbonate is obtained asa melt strand which, after cooling in a water-bath, was fed to agranulation.

The following reaction conditions were implemented (figures in % are %by weight, unless stated otherwise).

-   -   Na bisphenolate solution: throughput mixture of 1.270 kg/h of        bisphenol A and 2.59 kg/h of bisphenol TMC in aqueous alkaline        solution, concentration 15.0%,; 2.3 mol of NaOH per one mol of        bisphenol mixture; throughput therefore 25.75 kg/h of        bisphenolate solution    -   Phosgene: 1.789 kg/h (dissolved in the solvent mixture)    -   Solvent mixture: 24.38 kg/h        -   sodium hydroxide solution topped up (after the pumped            circulation reactor): 1.27 kg/h; concentration 46.7%    -   Chain terminator: 69.61 g/h of BUP, or 39.18 g/h of PHE    -   Catalyst EPP: 15.75 g/h; (3% in the solvent mixture)    -   Phosgene: 130 mol %, based on the total substance amount of        bisphenol    -   EPP: 1.0 mol %, based on the total substance amount of bisphenol    -   BUP or PHE: 3.3 mol %, based on the total substance amount of        bisphenol    -   Reaction temperature: 33° C.    -   Polycarbonate concentration: 15.0%    -   V number (viscosity number): 26.0±0.05    -   3-stage procedure

In the series of experiments, the influence of the chain terminatorunder otherwise identical reaction conditions was investigated. Thechain terminator was added such that the target viscosity (or V number)was reached.

The following continuous reaction conditions were realized, thepolycarbonates according to Examples 1 to 3 being prepared under theabovementioned reaction conditions. The chain terminators used can beseen from Table 1.

TABLE 1 Example Solvent Chain terminator Catalyst 1 SM BUP EPP 2 SM BUPEPP 3 SM PHE EPP MC: methylene chloride MCB: chlorobenzene SM: solventmixture (50% MC:50% MCB) BUP: para-tert-butylphenol PHE: phenol EPP:ethylpiperidine

The Tg is determined in accordance with ISO 11357, the HDT in accordancewith DIN ISO 306. The relative solution viscosity eta rel is determinedin methylene chloride (0.5 g of polycarbonate/l) at 25° C. The meltvolume rate is determined in accordance with ISO 1133.

The polycarbonates listed in Table 2 with the following properties wereobtained here:

TABLE 2 PC3 PC1 PC2 (comparison) Chain terminator BUP BUP phenolHydrolysable chlorine ppm 0.6 0.8 0.4 Phenolic OH ppm 80 50 60 Tg 2ndheating ° C. 207.2 208.9 205.5 GPC - Mw g/mol 30,135 29,220 30,292 GPC -Mn g/mol 10,776 9,716 9,515 GPC - U 1.8 2.01 2.18 Relative viscosity 25°C. 1.264 1.258 1.262 MVR 330° C./2.16 kg ml/10 min 6.5 6.5 6.5 IMVR 20′330° C./2.16 kg ml/10 min 6.5 6.7 6.3 Delta MVR/IMVR 20′ 0.0 0.2 −0.2Vicat VST B50 ° C. 204.1 205.2 201.3 Vicat VST B120 ° C. 204.9 205.6201.5 Notched impact kJ/m² 7s 7s 7s strength ISO 180/4A at roomtemperature RT

Comparison of the copolycarbonates PC-1 and PC-2 according to theinvention (copolycarbonates from the bisphenols BPA and TMC in theweight ratio of 33 to 67% by weight (molar ratio of 40 to 60 mol %) withtert-butylphenol as the chain terminator shows a significantly lowerinhomogeneity factor U than the phenol-terminated copolycarbonate PC-3(BPA/TMC, weight ratio likewise 33 to 67 wt. %). With the same MVR (meltvolume ratio) and therefore identical processing properties in theinjection moulding process, significantly increased glass transition andVicat temperatures are obtained, which corresponds to an improvement inthe heat distortion temperature.

Conversely, the same thermal and mechanical properties can already beachieved with the process according to the invention with less of theexpensive bisphenol TMC unit. The bisphenol BPA to TMC ratio can thus beshifted more in the direction of the less expensive bisphenol SPA.

It will be appreciated by those skilled in the art that changes could bemade to the embodiments described above without departing from the broadinventive concept thereof. It is understood, therefore, that thisinvention is not limited to the particular embodiments disclosed, but itis intended to cover modifications within the spirit and scope of thepresent invention as defined by the appended claims.

1. Copolycarbonates comprising: (i) a chain terminator structural unitof the formula (1):

wherein R1 and R2 each independently represent hydrogen or aC₁₋₁₈-alkyl, with the proviso that R1 and R2 are not simultaneouslyhydrogen; (ii) at least one diphenol unit of the formula (2)

wherein R³ represents a C₁₋₄-alkyl, R⁴ represents hydrogen orC₁-C₄-alkyl, and n represents 0, 1, 2 or 3; and (iii) at least onedihydroxyaryl compound of the formula (3)HO—Z—OH  (3) wherein Z represents a radical of the formula (3a)

wherein each R⁶ and each R⁷ independently represents a moiety selectedfrom the group consisting of H, C₁-C₁₈-alkyls, C₁-C₁₈-alkoxys, halogens,optionally substituted aryls or aralkyls, and X represents a moietyselected from the group consisting of —SO₂—, —CO—, C₁- to C₆-alkylenes,C₂- to C₅-alkylidenes and C₆- to C₁₂-arylenes, optionally condensed withfurther aromatic rings containing hetero atoms; wherein thecopolycarbonates have an inhomogeneity factor of: A) 1.3 to 2.5, whenthe copolycarbonates have a content of ≧50 mol % and <100 mol % of theat least one diphenol unit of the formula (2), based on total diphenols,and have an average molecular weight (weight-average) of 18,000 to35,000 g/mol; and B) 1.2 to 2.4, when the copolycarbonates have acontent of greater than 0 and less than 50 mol % of the at least onediphenol unit of the formula (2), based on total diphenols, and have anaverage molecular weight (weight-average) of 16,000 to 35,000 g/mol. 2.The copolycarbonates according to claim 1, wherein one of R1 and R2represents a hydrogen and the other represents a tert-butyl substituent.3. The copolycarbonates according to claim 1, wherein chain terminatorstructural unit of the formula (1) comprises a p-tert-butylphenolresidue.
 4. The copolycarbonates according to claim 1, wherein the atleast one diphenol unit of the formula (2) comprises a1,1-bis-(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane residue.
 5. Thecopolycarbonates according to claim 3, wherein the at least one diphenolunit of the formula (2) comprises a1,1-bis-(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane residue.
 6. Thecopolycarbonates according to claim 1, wherein the copolycarbonates havean inhomogeneity factor of: A) 1.4 to 2.3, when the copolycarbonateshave a content of ≧50 mol % and <100 mol % of the at least one diphenolunit of the formula (2), based on total diphenols, for linearcopolycarbonates having an average molecular weight (weight-average) of18,000 to 35,000 g/mol; and B) 1.2 to 2.0, when the copolycarbonateshave a content of greater than 0 and less than 50 mol % of the at leastone diphenol unit of the formula (2), based on total diphenols, forlinear copolycarbonates having an average molecular weight(weight-average) of 16,000 to 35,000 g/mol.
 7. The copolycarbonatesaccording to claim 1, having a general structure according to theformula:

wherein each R independently represents a C₁-C₄-alkyl, x and y eachindependently represent a number of 0 to 1 and the sum of x+y=1, and nis determined by molecular weight of the copolycarbonates.
 8. Thecopolycarbonates according to claim 7, wherein each R represents amethyl group, and x and y each independently represent a number of 0.02to 0.98.
 9. A composition comprising copolycarbonates according to claim1 and at least one additive selected from the group consisting of heatstabilizers, mould release agents, UV stabilizers, and combinationsthereof.
 10. The composition according to claim 9, wherein the at leastone additive comprises a compound selected from the group consisting oftris-(2,4-di-tert-butylphenyl) phosphite,tetrakis(2,4-di-tert-butylphenyl)[1,1-biphenyl]-4,4′-diyl-bisphosphonite,trisoctylphosphate, octadecyl-3-(3,5-di-tertbutyl-4-hydroxyphenyl)propionate,bis(2,4-dicumylphenyl)pentaerythritoldiphosphite,bis(2,6-di-tert.butyl-4-methylphenyl)penta-erythritoldiphosphite,triphenylphosphine, pentaerythritol tetrastearate, glycerolmonostearate, stearyl stearate, propanediol mono- or distearate,2-(2′-hydroxyphenyl)-benzotriazoles, 2-hydroxybenzophenones, esters ofoptionally substituted benzoic acids, acrylates, sterically hinderedamines, oxamides, 2-(2-hydroxyphenyl)-1,3,5-triazines, and mixturesthereof.
 11. A method comprising providing copolycarbonates according toclaim 1, and processing the copolycarbonates to provide an articleselected from the group consisting of moldings, extrudates, films,sheets and containers.
 12. A method comprising providing a compositionaccording to claim 9, and processing the composition to provide anarticle selected from the group consisting of moldings, extrudates,films, sheets and containers.
 13. An article prepared by the methodaccording to claim
 11. 14. An article prepared by the method accordingto claim
 12. 15. A process for preparing copolycarbonates according toclaim 1, the process comprising: (i) providing at least an alkylphenolof the general formula (1a)

wherein R1 and R2 each independently represent hydrogen or aC₁₋₁₈-alkyl, with the proviso that R1 and R2 are not simultaneouslyhydrogen, a diphenol of the general formula (2a)

wherein R³ represents a C₁₋₄-alkyl, R⁴ represents hydrogen orC₁-C₄-alkyl, and n represents 0, 1, 2 or 3; and at least onedihydroxyaryl compound of the formula (3)HO—Z—OH  (3) wherein Z represents a radical of the formula (3a)

wherein each R⁶ and each R⁷ independently represents a moiety selectedfrom the group consisting of H, C₁-C₁₈-alkyls, C₁-C₁₈-alkoxys, halogens,optionally substituted aryls or aralkyls, and X represents a moietyselected from the group consisting of —SO₂—, —CO—, C₁- to C₆-alkylenes,C₂- to C₅-alkylidenes and C₆- to C₁₂-arylenes, optionally condensed withfurther aromatic rings containing hetero atoms; and (ii) reacting thealkylphenol, the diphenol and the dihydroxyaryl compound in a continuousinterfacial reaction.